In the related art, a technique of wirelessly transmitting power between an underwater base station as a power transmission device and an underwater vehicle as a power receiving device by means of magnetic resonance is known (for example, refer to Patent Literature 1). The power transmission device includes a power transmission resonance coil, a balloon, and a balloon control mechanism. The power transmission resonance coil wirelessly transmits power to a power reception resonance coil of the power receiving device by means of magnetic resonance. The balloon houses the power transmission resonance coil. The balloon control mechanism causes the balloon to inflate during power transmission such that water between the power transmission resonance coil and the power reception resonance coil is removed.
In addition, an antenna device that transmits power and data to an IC-integrated medium by electromagnetic induction utilizing a frequency band of 13.56 MHz is known (for example, refer to Patent Literature 2). The antenna device includes: at least one power-fed loop antenna to which a signal current is supplied; and at least one non-power-fed loop antenna to which a signal current is not supplied, in which a signal current is generated in the non-power-fed loop antenna using a magnetic field generated from the power-fed loop antenna such that the communication range of the power-fed loop antenna expands.